Look for the word "Is" first - this is where your "=" goes. (In your problem, it actually says "is equal to".)
So now you know you have = 9.
The next key word on the left is "quotient" - that means divide. It says "quotient of a number and 5" - so we'll divide an unknown number (y in your problem) by 5.
Three less than means subtract 3 from that quotient.
So you need to start with the quotient: y/5 - 3 = 9.
hope it helps!